and Studi42, I found now the reason, why the caches got not cleaned correctly automatically. Joomla gives you per JFactory always the cache of the application. So I just replaced now all "getCache" by an own function (will be moved to vFactory, therefore already set to deprecated), so we use always the frontend cache folder.
the first maybe yes, the second is only to get info ( I need to push )
For pushing you need your own plugin or component. A push API is very likely to be unsecure. With a simple written plugin, using the VM infrastructure it is more safe to write a special task for your special purpose.
Unfortunately the real problem, is that virtuemart has many limits , sometimes seems really not built for ecommerce, cache problem over all . Then also problem with joomla, and you're on
The only "problem" is joomla. VM3 is much more scaleable than vm2. It works with a lot different type of caches. I think your main problem with vm2 were external 3rd party caching plugins. Vm3 is mainly cached by itself. It is a lot faster than vm2. It reduces the queries a lot, has a lot more db keys, and caches internal any bigger object (categories, products, manufacturer, vendor, cart, etc). The cart uses with 1 product around 40% less memory, when you have 50 products in the cart, then you notice the difference (vm2 was not able to handle that, almost any server just died). Takes maybe 10% of the memory (with 50 products), than before.
We also use on our demo store an nginx, which works with reverse proxy. It is very fast and there are no errors. We will use with our own store a CDN in future, so we will also solve any problems there.
The new version uses also a lot more ajax, in the FE (category browse, cart) and BE. And almost any entity has a language fallback now.
The future is a system, which works on Drupal, Joomla and WP :-)